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In this paper, we propose and experimentally demonstrate a novel compact multi-port multi-wavelength laser source (MP-MWL) for the optical I/O technology. The multi-wavelength DFB laser array is used for realizing the simultaneous emission of multiple wavelengths. The reconstruction equivalent chirp technique is used to design and fabricate the π-phase shifted DFB laser array to achieve precise wavelength spacing. The number of wavelengths is enlarged through the monolithically integrated wavelength routing architecture (WRA), and 64 optical carriers are obtained with 8 wavelengths in 8 output ports. The proposed MP-MWL has high mode stability and high uniform wavelength spacing. The side mode suppression ratio (SMSR) of each wavelength is more than 40 dB and the wavelength spacing is 100 GHz under 25 °C working environment. A semiconductor optical amplifier (SOA) is monolithically integrated into each output port to amplify the output power. The output power of each port exceeds 15 mW when the current injected into the SOA is 150 mA. Besides, the relative intensity noise (RIN) of all wavelengths is below -130 dB/Hz, and clear 25 Gb/s NRZ eye grams are obtained for the 64 optical carriers with the external lithium-niobate Mach-Zehnder modulator, with a total transmission rate of 1.6 Tbps. The superior performance of the proposed MP-MWL enables it to be a promising approach for the Tbps optical I/O links and high-density chip interconnection system.

To the best of our knowledge, the spectroscopic and highly efficient tunable multi-wavelength laser properties of Er3+,Yb3+,Pr3+ triple-doped BaLaGa3O7 crystals are demonstrated for the first time in this study. The maximum output power of 0.81 W at ∼2.7 μm was obtained under the absorbed pump power of 3.53 W with an optical-to-optical conversion efficiency of 22.9%. The slope efficiency is 27.0%. The results demonstrate that the triple-doped crystals with the sensitizer Yb3+ and deactivator Pr3+ can not only enhance the pump efficiency effectively but also suppress the self-terminating "bottleneck" effect of Er3+ so that the laser threshold is reduced and the laser efficiency is improved. The Er3+,Yb3+,Pr3+ triple-doped BaLaGa3O7 crystal is a promising candidate for high-efficiency mid-infrared laser devices. [ABSTRACT FROM AUTHOR]

We propose and experimentally demonstrate a compact and efficient photonic convolution accelerator based on a hybrid integrated multi-wavelength DFB laser array by photonic wire bonding. The photonic convolution accelerator operates at 60.12 GOPS for one 3 × 3 kernel with a convolution window vertical sliding stride of 1 and generates 500 images of real-time image classification. Furthermore, real-time image classification on the MNIST database of handwritten digits with a prediction accuracy of 93.86% is achieved. This work provides a novel, to the best of our knowledge, compact hybrid integration platform to realize the optical convolutional neural networks.

The radio-over-fiber (RoF) technique has gained a lot of interest recently, as the millimeter-wave signals can be generated and delivered in the optical domain with the advantages of low attenuation, high capacity, and being free from electromagnetic noise interference (EMI). In this paper, we propose and experimentally prove a self-start multi-wavelength laser source based on a distributed feedback laser diode (DFB-LD) for the RoF transport system. The self-start multi-wavelength laser source generates stable laser power with less than 0.18 dB power fluctuation and exhibits good stability. In order to estimate the transmission performance, data is externally modulated onto the multi-wavelength by a reflective semiconductor optical amplifier (RSOA) and transmitted through single-mode fiber (SMF). The experimental result proves that the proposed RoF transport system achieves error-free transmission and clear eye diagrams.

ObjectiveUltraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments.MethodsTwelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO2 laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements.ResultsDifferent laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO2 laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups.ConclusionSurface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO2 laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc.

Multi-wavelength laser absorption spectroscopy has the advantages of superior sensitivity, accuracy, and robustness for gas sensing applications, offering an opportunity for the development of high-performance laser-based hygrothermographs. However, accurate and fast determination of gas parameters from multiple spectral features can be quite challenging in the presence of large numbers of features, measurement noise, and increasing demands for real-time measurements. To address this challenge, we propose a transfer-learning-based multi-wavelength laser absorption sensor for the quantitative and simultaneous measurement of temperature and concentration of water vapor, with a focus on real-time monitoring of ambient temperature and relative humidity (RH). A spectral simulation based on the most-updated HITRAN database was employed as the dataset for model pre-training and transfer learning. The experimental dataset was obtained from absorption measurements using a distributed feedback laser that probed multiple water absorption features within the band of 7179-7186 c m -1 . To evaluate the sensor performance, mean absolute error, error distribution, and linearity were selected. In the presence of an insufficient experimental dataset for direct data training, the proposed transfer learning approach outperformed the traditional deep learning method with a lower prediction error of 0.14°C and 0.42% for temperature and RH, respectively, as compared to the values of 0.84°C and 0.66% obtained using the traditional deep learning method. Finally, the fast data post-processing performance of the proposed transfer learning approach was demonstrated in a field test against the conventional baseline fitting method.